1. Field of the Invention
The subject invention generally relates to a ceramic article. More specifically, the subject invention relates to a ceramic article for use in a metal matrix composite.
2. Description of the Related Art
Metal matrix composites (MMCs) are composite materials that comprise at least two constituents, one of which is a metal or an alloy. As compared to monolithic materials comprising a single constituent, MMCs have a higher strength-to-density ratio, a higher stiffness-to-density ratio, better fatigue resistance, and higher strength at elevated temperatures. MMCs also have a higher wear resistance than monolithic materials. As such, MMCs are typically useful for applications requiring wear resistance and strength, e.g., brakes.
MMCs are produced by augmenting a metal matrix with reinforcing materials. The metal matrix and reinforcing materials are typically chosen to optimize mechanical and physical properties of the MMCs. Numerous combinations of metal matrices and reinforcing materials are known in the art. Effective metal matrices comprise aluminum, magnesium, titanium, copper, zinc, and superalloys. Effective reinforcing materials comprise boron carbide, silicon carbide, alumina, and graphite, and are available in the form of continuous fibers, discontinuous fibers, particles, and whiskers.
One method of producing MMCs includes infiltrating a ceramic article with the metal or alloy to form the MMC. Ceramic articles are often a fabric or prearranged fibrous configuration of reinforcing materials that are produced prior to metal infiltration.
Many existing ceramic articles comprise reinforcing materials oriented in only two dimensions. As such, many existing ceramic articles suffer from fatigue and/or failure in a third, non-reinforced dimension and do not exhibit uniform strength in three dimensions.
Additionally, many existing ceramic articles comprise small reinforcing materials to enable consistent mixing during ceramic article formation. However, consistent mixing often becomes difficult as the size of reinforcing materials decreases. Small reinforcing materials also often limit the mechanical and physical properties, such as wear resistance, of MMCs including existing ceramic articles.
Many existing ceramic articles also exhibit inconsistent density as a result of inconsistent mixing. Since consistent mixing ideally includes both dispersion of reinforcing material agglomerates and uniform distribution of reinforcing materials throughout the ceramic article, inconsistent mixing results in nonuniform distribution of reinforcing materials in existing ceramic articles and contributes to ceramic articles having inconsistent density, physical properties, and performance. Ceramic articles having inconsistent density wear more readily than ceramic articles having consistent density and are not useful for applications requiring high wear resistance. Additional reinforcing materials must often be added to existing ceramic articles after formation to remedy such inconsistent density, which increases production costs of existing ceramic articles.
Further, many existing ceramic articles are heavy due to necessary additional reinforcing materials included to compensate for inconsistent mixing of reinforcing materials. Heavy ceramic articles are often not suitable for applications requiring lightweight components, such as automotive or aeronautical applications.
Finally, many existing ceramic articles suffer from weak points caused by entanglement and conglomeration of reinforcing materials. Ceramic articles including entanglements and conglomerations are not as strong and stiff as ceramic articles free from such weak points. MMCs formed from ceramic articles including entanglement and conglomeration also suffer from inadequate metal infiltration due to blockages caused by such entanglement and conglomeration of reinforcing materials.
Due to the inadequacies of existing ceramic articles, there remains an opportunity to provide a ceramic article that improves upon existing ceramic articles for use in metal matrix composites.